中文摘要：

萨拉乌苏流域位于黄土高原与鄂尔多斯沙漠之间,是北方黄土与沙漠过渡带的重要组成部分,对气候环境变化相当敏感。选择该流域典型沉积剖面（滴哨沟湾剖面）,研究剖面Nd-Sr同位素组成变化特征,揭示沙漠—黄土过渡带物质来源变化规律。结果表明：①风成粗颗粒（〉75μm）由鄂尔多斯中西部高地风蚀所致,河湖相粗颗粒主要由下覆风成沉积物水蚀改造而来;②∣ΔεNd（0）∣≤1的风成细颗粒（〈75μm）基本上来自鄂尔多斯中西部高地的风化剥蚀和粗颗粒的就地改造,而∣ΔεNd（0）∣〉1的风成细颗粒有更复杂的物质来源;③城川组和中下部萨拉乌苏组的河湖相细颗粒由黄土高原的水土侵蚀提供,而萨拉乌苏组上部遭受了来自鄂尔多斯沙漠中东部风成细颗粒的干扰。这项研究对正确理解沙漠—黄土过渡带的演化有重要意义。

英文摘要：

The Salawusu Valley is located in a zone between the Loess Plateau and the Ordos Desert, and it is an important part of the desert-loess ecotone in north China and is very sensitive to climatic and environmental changes. In this study, the Dishaogouwan profile, a typical sedimentary sequence in the Salawusu Valley, was chosen as the study area to investigate the isotopic profiles and try to reveal the variation of sediment sources in the desert- loess ecotone. The results are as follows： （1） Coarse eolian deposits （ 〉 75 μm） came from wind erosion of the highlands in the central-western Ordos, and coarse fluvial-lacustrine deposits originated mainly from water erosion of underlying eolian deposits ; （2） Fine eolian deposits （ 〈 75μm） with absolute ΔεNd （0） values≤ 1 originated ba- sically from the wind erosion of the highlands in central-western Ordos and the refining of coarse particles in situ, but fine eolian deposits with absolute ΔεNd （0） values 〉 1 came from more complex sources; （3） Fluvial-lacustrine fine deposits of the Chengchuan and middle-lower Salawusu formations came from water erosion in the central Loess Plateau, but the deposits of the upper Salawusu formation were significantly disturbed by eolian fine particles from the central-eastern Ordos Desert. This study is very helpful for understanding the evolution of the desert-loess eco- tone in north China.